KR101921348B1 - Lithium ion cell having improved aging behavior - Google Patents

Abstract

The present invention relates to a formed secondary electrochemical cell comprising at least one positive electrode containing a metal compound capable of reversibly incorporating and releasing lithium in the form of ions, lithium reversibly incorporated in the form of ions And at least one negative electrode containing a releasable carbon compound and / or a metal and / or a semi-metal that can be alloyed with lithium, a negative electrode capable of passing when lithium ions move between at least one positive electrode and at least one negative electrode Wherein the capacity of at least one cathode for absorbing lithium is greater than the capacity of at least one anode and wherein at least one of the cathodes is in contact with the electrolyte, Having a capacity greater than the capacity required to absorb the total mobile lithium contained therein, said mobile lithium being capable of absorbing lithium Is contained in the battery in an amount exceeding the capacity of at least one positive electrode. The present invention also relates to a battery having at least one such battery and a method for manufacturing such a battery.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lithium ion battery having improved aging behavior,

The present invention relates to a secondary electrochemical cell and relates to a battery comprising at least one such battery and a method for manufacturing such a battery.

The term " battery " inherently refers to a plurality of electrochemical cells connected in series within the housing. Today, however, a single electrochemical cell is often referred to as a battery. During the discharge of the battery, an energy-supplying chemical reaction consisting of two electrically connected, but physically separated, subreactions occurs. One partial reaction that occurs at a relatively low redox potential proceeds at the negative electrode and a partial reaction at the relatively high redox potential proceeds at the positive electrode. During the discharge, the electrons are liberated from the cathode by the oxidation process, which causes the flow of electrons through the external load to the anode, which absorbs the corresponding amount of electrons. Therefore, the reduction process occurs at the anode. Simultaneously, an ion current (ion current) corresponding to the electrode reaction is generated in the cell. This ion current is obtained using an ion-conducting electrolyte. In secondary batteries and batteries, this discharge reaction is reversible and therefore it is possible to reverse the conversion of chemical energy generated during discharge into electrical energy. When the terms anode and cathode are used herein, the names of the electrodes are generally determined according to their discharge function. In this battery, therefore, the cathode is the anode and the anode is the cathode.

The dischargeable charge of the battery, which greatly varies depending on the discharge state, is referred to as the capacity (unit, Ah). The specific charge (unit Ah / Kg) or the charge density (unit Ah / L) can be calculated for the number of free or received electrons and / or ions per unit mass or volume, . In this context, therefore, reference is also made to the specific capacity of the electrode and battery, also indicated in units of Ah / kg. The large potential difference between the cathode and the anode causes a high value for specific energy (unit Wh / kg) or energy density (unit Wh / L), together with electrode material with high specific charge or charge density. When operating a battery, the rate of electron transfer and ion transfer inside the battery, in particular, the rate of ion movement at the phase interface in the electrode, limits the power. The associated properties of the battery can be taken from the core specific power (unit W / kg) and power density (unit W / l).

Among secondary batteries and batteries, lithium ion batteries have a relatively high energy density. These batteries generally have a composite electrode comprising an electrochemically active component together with an electrochemically inactive component. Possible electrochemically active components (often referred to as active materials) for lithium ion batteries are, in principle, all materials that absorb and release lithium ions. In this regard, graphite carbon or non-graphitic carbon materials which are capable of intercalating lithium, especially carbon based particles, for example lithium, are the latest technologies. In addition, metallic or semi-metallic materials that can be alloyed with lithium may also be used. For example, tin, antimony, and silicon elements can form an intermetallic phase with lithium. For the anode, the presently industrially applicable active material is lithium cobalt oxide (LiCoO ₂ ), LiMn ₂ O ₄ spinel (LiMn ₂ O), lithium iron phosphate (LiFePO ₄ ) and derivatives, such as LiNi _1/3 Mn _{1 / 3} Co _1/3 O ₂ or LiMnPO ₄ . In general, all electrochemical active materials are contained in the electrode in the form of particles.

As an electrochemically inactive component, among other things, it can refer to an electrode binder and a current collector. Electrons are supplied or discharged from the electrodes through the current collector. On the other hand, the electrode binder ensures the mechanical stability of the electrode and, on the other hand, ensures contact of the particles constituting the electrochemical active to each other and to the current collector. Likewise, the conductivity-enhancing additive, which can be included in the generic term " electrochemically inactive component ", can contribute to improved electrical contact of the current collector and electrochemically active particles. All electrochemically inactive components must be electrochemically stable at least within the potential range of their respective electrodes and chemically inert to the common electrolyte solution. The common electrolyte solution is an organic solvent, e. G., An ether of carbonic acid and a lithium salt in the ester, e. G., A solution of lithium hexafluorophosphate.

The above-mentioned carbon-based active material for a negative electrode has a reversible maximum ca. Enabling a specific capacity of 372 Ah / kg. Even higher storage capacities of up to 4200 Ah / kg are exhibited by the abovementioned metallic or semi-metallic materials which can be alloyed with lithium. Alternatively, the aforementioned capacity of the cathode material is only in the range of 110 Ah / kg to 250 Ah / kg. Thus, in order to meet the actual capacity of the electrode in the most optimal manner, an attempt is made to balance the material of the anode and the cathode in terms of quantity.

In this context, it is particularly important for the cover layer to be formed on the surface of the electrochemical active material in the anode during the first charge / discharge cycle (so-called formation) of the secondary lithium ion battery (D. Aurbach, H. Teller, M. Koltypin, E. Levi, Journal of Power Sources 2003, 119-121, 2). The cover layer is referred to as a " Solid Electrolyte Interphase " (SEI) and is typically composed primarily of electrolyte deposition products as well as a certain amount of lithium that is no longer available for further charge / discharge reactions . Ideally, the SEI is permeable only to very small amounts of lithium ions and prevents further direct contact of the electrolyte solution with the electrochemical active material in the anode (BV Ratnakumar, MC Smart, S. Surampudi, Journal of Power Sources 2001, 98, 137). So far, the creation of SEI has had a positive effect. However, the loss of mobile lithium due to the SEI-generation has a negative effect. Typically, during the first charging process, there is a loss of approximately 10% to 35% of moving lithium depending on the type and amount of active material and electrolyte solution applied. Likewise, the achievable capacity decreases by the percentage rate. This loss due to formation must be taken into account when balancing the anode and cathode.

Besenhard, M. Winter, M. Wohlfahrt-Mehrens, C. Vogler, A. Hammouche, Journal of Power Sources, 2005, 269-281, 147 참조). 전기화학적 활물질의 표면 상의 SEI 층의 두께는 점점 더 증가하며, 종종 전지 임피던스의 상당한 증가를 초래한다. 이에 추가로, 이동 리튬의 증가하는 손실이 고려되어야 한다. 이러한 효과는 영향 받는 전지의 점진적으로 감소하는 용량 및 전력을 초래한다. 전지가 노화된다.During subsequent cycles, generally only a small amount of lithium loss is present. However, after a larger number of cycles, this small amount of lithium loss becomes important and may even be the most important parameter of cell aging (J. Vetter, P. Novak, MR Wagner, C. Veit, K. C. Moller, JO

Besenhard, M. Winter, M. Wohlfahrt-Mehrens, C. Vogler, A. Hammouche, Journal of Power Sources, 2005, 269-281, 147). The thickness of the SEI layer on the surface of the electrochemical active material increases more and more, often resulting in a significant increase in battery impedance. In addition, an increasing loss of mobile lithium should be considered. This effect results in a progressively decreasing capacity and power of the affected cells. The battery ages.

Using over-lithiated cathode materials with carbonaceous-based anodes may cause this phenomenon to decrease, but in some cases can lead to impairment of safety. Whether there is a stability problem depends on the ratio of the maximum capacity of the anode to the capacity of the anode after formation. For example, the maximum specific capacity of the anode per graphite unit is 372 mAh / g. Therefore, it is theoretically possible to combine the anode with a cathode containing a certain amount of mobile lithium ions corresponding to 372 + 15% to 427 mAh / g, when 15% of the mobile lithium is lost due to SEI generation during the formation process . However, if the lithium loss is less significant during the formation, metallic lithium may be undesirably deposited on the anode. To prevent this, the anode of a lithium ion battery is generally over-dimensioned.

In addition, the problem is that the lithiation of the above-mentioned active material is caused by a significant increase in volume. Therefore, the volume of graphite particles can be increased up to 10% when absorbing lithium ions. The volume increase is greater for the aforementioned metallic and semi-metallic storage materials. For example, when lithium, tin, antimony, and silicon are lithiated, the volume expansion during the first charge cycle can be up to 300%. When lithium ions are released, the volume of each active material decreases again, which results in high mechanical stresses in the particles that make up the active material and, in some cases, can lead to shifting in the electrode structure. In some cases, the relative mechanical stresses of the electrodes to a significant extent result in contact loss between adjacent particles making up the active material, which negatively affects the capacity and life cycle of the affected battery.

It is an object of the present invention to provide a lithium ion battery having improved aging performance with no or minimal occurrence of the above problems.

This object is achieved by an electrochemical cell having the features of claim 1, a battery having the features of claim 6, and a method having the features of claim 7. Preferred embodiments of the electrochemical cell according to the present invention are shown in dependent claims 2 to 5. A preferred embodiment of the method according to the invention can be found in dependent claims 8-10. The description of all claims is incorporated by reference into the present disclosure.

The electrochemical cell according to the present invention is a secondary cell which is a rechargeable battery as mentioned above. In addition, the battery according to the present invention is an already-formed cell, which, according to the description above, has already undergone at least one complete charge / discharge cycle, so that the described " solid electrolyte interphase & Which means that the loss of lithium in subsequent cycles is only a relatively small amount. The formed cell is structurally different from the non-formed cell. In the present invention, the formed cell is particularly characterized in that the loss of lithium in the cell during subsequent cycles due to SEI generation already generated during the first charge / discharge cycle is less than 0.5%, preferably less than 0.25%, especially less than 0.1% (In each case based on the total available amount of mobile lithium in the pre-cycle cell).

An electrochemical cell according to the invention comprises at least one anode, at least one cathode, an electrolyte, and so-called " mobile lithium ".

The at least one anode contains at least one metal compound, and the at least one metal compound can reversibly incorporate and release lithium in the form of ions. In addition, it is customary to include, in some cases, at least one electrode binder, one conductivity additive, and further additives. Suitable binders and additives are well known to those of ordinary skill in the art.

Preferably, at least one compound is a lithium metal oxide or a lithium metal phosphate compound, in _{particular, LiCoO 2, LiMn 2 O 4} , LiFePO 4, LiNi 1/3 Mn 1/3 Co 1/3 O 2, LiMnPO 4 or the A mixture of two or more of the compounds.

The at least one negative electrode contains at least one carbon compound capable of reversibly incorporating or releasing lithium in the form of ions. Alternatively or additionally, however, at least one negative electrode may also contain at least one metal and / or a semi-metal which can be alloyed with lithium.

In addition to the active material, in some cases, at least one negative electrode generally comprises at least one electrode binder, one conductivity additive, and further additives. Suitable binders and additives are known to those of ordinary skill in the art. A particularly preferred carboxymethylcellulose-based binder is described in WO 2009/012899. The contents of which are incorporated herein by reference.

As the carbon compound, it is preferable that at least one negative electrode contains a graphitizing carbon compound. As metals and / or semi-metals that can be alloyed with lithium, it is preferred that the electrode contains at least one member selected from the group consisting of aluminum, silicon, antimony, tin, and cobalt. As mixtures, tin / antimony mixtures or tin-cobalt mixtures are optionally preferred.

In a particularly preferred configuration, the at least one negative electrode comprises a carbonaceous compound capable of intercalating and, specifically, a combination of a metal and / or a semi-metal which can be alloyed with lithium as a mixture of graphitic carbon particles and silicon particles do. The particles are preferably included in a binder matrix composed of suitable carboxymethylcellulose.

A composite electrode containing 20 wt% (weight percent) silicon and 60 wt% graphitic carbon as the active material and 20% electrochemical inactive material (binder and conductivity additive) (4200 Ah / kg * 0.2) + (372 Ah / kg * 0.6), which has a specific capacity of 1060 Ah / kg. By varying the ratio of silicon, the capacity required to store lithium can be flexibly adjusted without substantially increasing the mass of the required active material.

Through the electrolyte contained in the battery according to the invention, lithium ions can migrate between at least one anode and at least one cathode. Preferably, the electrolyte is a solution of a suitable conductive salt, such as lithium hexafluorophosphate. As the solvent, preferably an organic solvent is used, in particular, an ether or an ester compound of carbonic acid is used.

In the present invention, " mobile lithium " means lithium available for incorporation and release processes at the electrode. As described above, during the formation of the secondary lithium ion battery, the above-mentioned SEI is produced, and irreversibly binds a portion (up to 35%, see above) of lithium initially contained in the battery. do. The lithium is then no longer available for further charge / discharge reactions. Alternatively, " moving lithium " is a fraction of lithium in the cell and is still available for reversible incorporation or release processes in the electrode after formation.

In particular, the battery according to the invention is characterized by a combination of the following features:

1. The capacity of at least one cathode for absorbing lithium is higher than the capacity of at least one anode.

2. At least one negative electrode has a capacity greater than the capacity required to absorb the total moving lithium contained in the cell.

3. The moving lithium is contained in the battery in an amount exceeding the absorption capacity of the at least one anode.

A combination of the above features will be described in detail starting from the feature 1 below.

Since it is a known art in the art to over-dimension the cathode relative to the opposing anode in order to prevent metallic lithium from being deposited on the anode during charging, Not new. However, in the case of the electrodes according to the invention, this is not an option, since at the same time at least one cathode is dimensioned to a size sufficient to absorb all the moving lithium contained in the cell (feature No. 2). Therefore, it is not possible to overcharge at least one cathode with lithium. At the same time, however, the battery according to the invention contains more mobile lithium than can be absorbed by the at least one anode (feature No. 3). In other words, the battery according to the invention comprises a " reservoir " or " pool " of mobile lithium, whereby the minor lithium losses described above occurring during post-formation operations can be continuously balanced. Therefore, the capacity and power of the battery according to the present invention is kept stable for a greater number of cycles compared to the battery known in the prior art.

Preferably, the mobile lithium is contained in the battery according to the invention, also in the form of lithium ions and, if desired, also in reduced metallic form. When the battery according to the present invention is fully charged, lithium ions are substantially all incorporated into at least one over-dimensioned cathode. During operation, lithium ions are distributed between at least one negative electrode and at least one positive electrode. Lithium may be provided in the form of a reduced metal when alloyed with one of the above-mentioned metals and / or semi-metals that may be alloyed with lithium, particularly on the anode side. Also in this form, it is available for a reversible incorporation and release process at the electrode. When discharging the battery according to the present invention, the alloyed lithium can be oxidized. Thereafter, the final lithium ions can migrate to the cathode.

In a preferred embodiment, the aforementioned capacity of at least one cathode for absorbing lithium is 1.2 times, preferably 1.4 to 2.5 times greater than the capacity of at least one anode.

The capacity of at least one negative electrode is preferably at least equal to the total amount of mobile lithium contained in the battery, and particularly preferably at least 1.05 times, preferably 1.1 to 10 times, Two times higher.

The amount of mobile lithium in the battery is at least 1.1 times, particularly preferably 1.2 to 2 times greater, than the capacity of at least one anode for absorbing lithium.

The mixing ratio between the carbon compound and the metal and / or the semi-metal which can be alloyed with lithium in the anode is in some cases preferably from 20: 1 to 1:20, particularly preferably from 20: 1 to 1: 1 Weight used in each case).

Likewise, each battery comprising at least one electrochemical cell according to the invention as described above is the subject of the present invention. For example, a battery according to the present invention may be provided in the form of a composite of a flat electrode and an electrolyte-permeable separator. In batteries according to the present invention, such composites are preferably provided in a stacked arrangement or in wound form.

To manufacture such a battery, in particular, a method described below can be used, and the method is likewise included in the invention disclosed herein.

In this method, at least one anode of the type described above, at least one cathode of the type described above, and electrolytes of the type described above are combined into one electrochemical cell. The battery made in this way is then formed, i. E., Undergoes at least one complete charge / discharge cycle.

In this case, the process according to the invention is characterized in particular by:

In terms of the capacity for absorbing lithium, at least one cathode is dimensioned larger than at least one anode.

Lithium is introduced into the cell in an amount that exceeds at least 1.2 times the capacity of the at least one anode for absorbing lithium.

In terms of the capacity for absorbing lithium, at least one negative electrode is dimensioned to a size sufficient to absorb the total lithium contained in the battery after formation.

Related to the over-dimension of at least one cathode relative to at least one anode, and in relation to the amount of mobile lithium contained in lithium, particularly after formation, of the method according to the invention In view of the preferred embodiment, reference is made to the above description relating to a battery according to the invention.

The amount of lithium introduced into the battery is 1.2 to 2 times greater than the capacity of at least one anode for absorbing lithium.

In a preferred embodiment, lithium is introduced into the cell at least partially through at least one anode. In particular, this may be achieved using over-lithiated cathode materials. For example, an over-lithiated oxidizing compound, such as LiNi _0.425 Mn _0.425 Co _0.15 O ₂ , can be reversibly lithiated or de- _{lithized in} subsequent cycles, Lt; RTI ID = 0.0 > ions. ≪ / RTI > During the first charging process, the excess lithium ions may begin to migrate to the over-dimensioned anode.

Another option for introducing lithium through at least one anode is to add metallic lithium, especially passivated metallic lithium, as at least one anode. For example, it is possible to passivate lithium particles by covering the surface of lithium particles with a thin layer of lithium phosphate, a wax or a polymer layer. Suitable methods are described in WO 2008/143854, WO 2009/029270 and WO 2008/045557. The contents of these documents are incorporated herein by reference in their entirety. Metallic lithium can be introduced into the anode in a relatively insignificant manner because the anode for the lithium ion battery is generally treated in a non-aqueous atmosphere.

Another option for introducing lithium into the cell is to introduce lithium at least partially through the electrolyte, in particular by using a conductive salt that can liberate lithium ions at the anode. Lithium azide (LiN ₃ ) is an example of such salts.

In another preferred embodiment, lithium is introduced into the cell at least partially through one negative electrode. This may be accomplished by pre-lithizing the at least one cathode prior to combining the at least one cathode with the at least one anode. In the simplest case, for example, at least one cathode is connected and charged to an electrode made of metallic lithium. The charged at least one electrode is then connected to at least one anode.

Alternatively or additionally, it is possible to use a compound capable of liberating lithium ions, in particular an anode material, for at least one negative electrode containing a transition metal nitride of the formula Li _3-x M _x N have. These materials promise high, stable, and reversible capacity, but further include de-lithiable lithium in the structure rather than being able to reversibly incorporate or release it. A disadvantage of this material is the lack of cycle stability and high hydrolysis sensitivity (Yu Liu, Kumi Horikawa, Maniko Fujiyosi, Nobuyuki Imanishi, Atsushi Hirano, Yasuo Takeda, Electrochemical Acta 49, 2004, 3487 -3496 and Y. Takeda, M. Nishijima, M. Yamahata, K. Takeda, N. Imanishi, O. Yamamoto, Solid State ionics 130, 1999, 61-69).

Another option for introducing lithium into the cell is the use of the above-mentioned metallic lithium, especially electrode materials containing the above-mentioned passivated metallic lithium. These particles are generally capable of being mixed in both the cathode and the anode materials.

Where appropriate, passivated lithium may be used in the fabrication of electrodes to be treated in an aqueous environment. However, it is more preferable to add metallic lithium to the electrode after fabrication, particularly in the aqueous atmosphere after drying of the electrode. Thus, for example, after the cathode treated in an aqueous atmosphere has dried, it may be desirable to apply metallic lithium to the surface of the cathode. The application of the metallic lithium can be initiated, for example, by a foil which functions as a carrier for the passivated lithium particles mentioned above and which can be lamily contacted to the surface of the electrode.

In the case of introduction on the anode side, passivated lithium is already located in the anode. Like the previously mentioned metal and / or semi-metal alloyed lithium, the passivated lithium is oxidized during operation and can liberate lithium ions, which can migrate to the cathode. In the case of introduction onto the cathode side, generally, in the first charge / discharge cycle of the cell, passivated lithium is introduced into the above-mentioned additional capacity of the anode.

At this time, all the aforementioned preferred procedures for introducing lithium into the cell may be used alone or in combination with other procedures.

As already mentioned, a major advantage of the described method of balancing the electrodes of a lithium ion battery with a high capacity anode material affects the aging performance. Some other significant benefits will be summarized as follows.

Tin, antimony, or a combination of these materials and a carbon-based material, as the at least one cathode has a generally larger capacity, generally greater than the capacity required to absorb the total moving lithium contained in the cell. It is common that the high-capacity anode material which is preferably used according to the present invention based on the mixture is not completely lithiumated. In this way, the material only receives relatively little mechanical stress during the charging and discharging process, thus preventing irreversible deactivation of the active material particles, which otherwise could lose electrical contact with the electrodes due to the large volume change due to lithiation do.

For electrodes containing silicon, this means that during operation the highest level of lithium ionization (Li ₂₂ Si ₅ ) and the maximum achievable capacity of 4200 Ah / kg associated therewith are not reached. Basically, the use of silicon alloy capacity for formation charging is possible within 600Ah / kg to 4200Ah / kg. However, in order to produce a lithium pool, the amount of lithium, which generally corresponds to a 10 to 80% lower capacity value, is de-lithiated in subsequent cycles. The standard values likewise apply to silicon which is treated to be a composite electrode in combination with further active materials, such as carbon compounds, metals or semi-metals that can be alloyed with lithium, such as tin, antimony, and aluminum.

In addition, a higher discharge voltage of the battery is ensured by the manner described above for balancing the electrodes. Because of the fact that the anode material undergoes complete lithiation once, but never completely de-lithiated, there is always a lithium reserve in the anode, which is why the discharge voltage for the entire battery is always higher overall.

Many cathode materials that are combined with high capacity anodes using conventional methods do not allow complete de-lithiation of the lithium ions contained in the cathode material. An example of such a material is a host material of the type LiMO ₂ (M = Co, Ni). The most common of the cathode materials is lithium cobalt oxide having an? -NaFeO ₂ structure. According to the stoichiometry of Li _0.5 CoO ₂ , the potential is 4.2V vs. Li < + > +, followed by liberation of oxygen and a change from a cubic structure to a hexagonal structure. A further critical aging process will occur when moving lithium is lost due to the creation of a new SEI in a battery that balances according to the prior art. Since the switch-off criterion of the battery during charging is guaranteed by the nominal voltage of the battery, if the amount of mobile lithium is too low, an additional required amount of lithium is released from the cathode. But it can be achieved only by reducing to less than Li _0.5 CoO ₂ structure ratio of lithiated lithium possible form of the further amount of cathode active material that is accompanied by irreversible destruction. By generating a lithium pool in the battery, the loss of moving lithium is counterbalanced by the lithium paste, so that the occurrence of the aging effect can be prevented. The Li _0.5 CoO ₂ structure will not be lowered until the lithium pool is depleted.

Additional features of the invention will be apparent from the following description of the drawings and preferred embodiments, taken in conjunction with the dependent claims. In this case, the individual features may be embodied in combination in each case alone or in one embodiment of the invention. As noted, the preferred embodiments are for purposes of illustration only and are for a better understanding of the invention and are not to be construed in any way as limiting.

Figure 1 schematically illustrates the principles of the present invention.

The height of the column shown in Fig. 1A corresponds to the capacity of the electrode of the battery according to the present invention. In addition, the amount of lithium contained in the electrode can be known from the ordinate. (For example, containing a mixture of silicon and graphite as an active material) is considerably larger than the capacity of the cathode (for example, containing a lithium metal oxide compound, for example, lithium cobalt oxide as an active material). The anode already contains a certain amount of lithium introduced in the previous step by mixing the passivated lithium with the aforementioned active material. The amount of lithium contained in the anode appears as a shaded area. The total amount of lithium contained in the electrode significantly exceeds the capacity of the cathode capable of receiving lithium.

In Figure IB, the process during the first battery charge of the electrode shown in Figure 1A is shown. The cathode is de-lithiated during charging of the cell. Lithium ions move to the anode (in the arrow direction). During the generation of the SEI, a portion of the lithium ion is consumed. The amount of lithium ions consumed appears on the anode side at the bottom of the column (see lower hatched area). However, the amount of lithium ion consumed is smaller than the amount of lithium introduced into the anode in the previous step (upper hatched region).

In Figure 1C, the amount of lithium lost due to SEI generation appears below the horizontal axis, as it is no longer available for charging or discharging the reversible battery. The discharging procedure is shown following the charging shown in Fig. 1B. It is possible to completely recharge the anode with lithium ions, since the lithium impregnated in the SEI can be compensated by the lithium introduced into the anode in the previous step. The difference? Between the amount of lithium ion confined in the SEI and the amount of lithium introduced into the anode in the previous step is maintained as the lithium reserve of the anode.

In FIG. 1D, the filling procedure is shown after the formation is complete. In the event of additional loss of lithium ions, the ions are replaced by lithium stockpiles. Before the lithium stockpile is depleted, the amount of available lithium for the incorporation and release procedures will not decrease.

2A shows the efficiency of the charging capacity with respect to the discharging capacity (lower curve) and the discharging capacity of the first battery as a function of the number of cycles. The first battery serves as a reference for a battery according to the present invention.

The anode of the first battery was a mixture of 8 wt% sodium carboxymethylcellulose, 10 wt% conductivity additive (a mixture of conductive carbon black and carbon nanofiber) and 20 wt% silicon (medium particle size 30-50 nm) And 62 wt% of graphite carbon. Water was used as the process solvent (4 g of water per gram of electrode material). The paste was applied as a thin layer on a copper foil which served as a current collector.

The cathode of the first battery was constituted by a thin layer of electrode material coated on an aluminum foil which also functioned as a current collector. When the cathode was produced, the cathode paste consisted of 5 wt% polyvinylidene fluoride-hexafluoropropylene polymer binder, 7 wt% conductivity additive (conductive carbon black), and 88% LiCoO ₂ as an electrochemical active material. As a treatment solvent, N-methyl-2-pyrrolidone was used (5 g of N-methyl-2-pyrrolidone for 4 g of electrode material).

An organic electrolyte was used as an electrolyte containing a carbonate-based electrolyte solvent and lithium hexafluorophosphate as a conductive salt.

The anode capacity was 0.393 mAh (at a specific capacity of approximately 1070 mAh / g). The capacity of the cathode was 0.240 mAh. The cell was controlled through the cell voltage, charged and discharged in the range of 3V to 4.2V, and the nominal cell capacity was 0.240 mAh. Two cycles of 0.1 C and the next cycle of 0.5 C were performed, where 1 C corresponds to a current of 0.240 mA. As an additional condition, the cathode was operated to a maximum voltage of 4.2 V and the anode was operated to a maximum voltage of 1.5 V.

2B shows the discharge capacity (lower curve) of the second battery according to the present invention and the efficiency of the charging capacity with respect to the discharge capacity according to the number of cycles.

In this case, the anode also comprises 8 wt% sodium carboxymethylcellulose, 10 wt% conductivity additive (mixture of conductive carbon black and carbon nanofiber), 20 wt% silicon (medium particle size 30-500 nm) and 62 wt% graphite Lt; RTI ID = 0.0 > carbonaceous < / RTI > Water was used as the treating solvent (4 g of water per gram of electrode material). The paste was applied as a thin layer on a copper foil functioning as a current collector.

However, unlike the first battery, a lithium pool was formed in the anode by switching the anode to an electrode made of metallic lithium and charging the anode to 70% of a maximum capacity of about 1250 mAh / g. After the pre-lithiation, the cathodes corresponding to the anode were combined.

To prepare the cathode, a 5 wt% polyvinylidene fluoride-hexafluoropropylene polymer binder, 7 wt% conductivity additive (conductive carbon black), and 88% LiCoO ₂ as the cathode material, as in the case of the first battery A paste was used. The paste was applied in an aluminum foil functioning as a current collector and dried to form a thin electrode layer thereon. As a treatment solvent, N-methyl-2-pyrrolidone was used (5 g of N-methyl-2-pyrrolidone for 4 g of electrode material).

An organic electrolyte was used as an electrolyte containing a carbonate-based electrolyte solvent and lithium hexafluorophosphate as a conductive salt.

The pre-lithiated anode has a capacity of 0.404 mAh (at a specific capacity of about 1070 mAh / g). This was combined with a cathode having a capacity of 0.253 mAh. Thus, the fabricated cells were controlled through the cell voltage, charged and discharged within the limits of 3V and 4.2V, respectively, and the nominal cell capacity was 0.253 mAh. Two cycles of 0.1 C and a subsequent cycle of 0.5 C were performed, where 1 C corresponds to a current of 0.240 mA. For further conditions, the cathode was operated to a maximum voltage of 4.2 V, and the anode operated to a maximum voltage of 1.5 V.

Despite the same components, the first battery and the second battery showed full performance, as shown in Figures 2A and 2B. Generating a lithium pool on the anode significantly delayed aging of the second battery.

Claims (10)

As a secondary electrochemical cell formed,
At least one positive electrode containing a metal compound capable of reversibly incorporating and releasing lithium in the form of ions,
A mixture of a graphitizable carbon compound capable of reversibly incorporating and releasing lithium in the form of ions and a metal capable of being alloyed with lithium or a mixture of the graphitic carbon compound and a semi- At least one negative electrode containing a metal and a mixture of said semi-
An electrolyte capable of passing through when lithium ions move between at least one anode and at least one cathode, and
A mobile lithium available for incorporation or release processes at the electrode,
Wherein at least one negative electrode for absorbing lithium has a capacity larger than that of at least one positive electrode and at least one negative electrode has a capacity larger than a capacity required for absorbing the entire moving lithium contained in the battery, Is contained in the battery in an amount exceeding the capacity of the at least one anode for absorbing lithium and the additional moving lithium is supplied by the metal lithium or through the cathode electrode by the pre- battery. The secondary electrochemical cell of claim 1, further comprising the mobile lithium in the form of lithium ions or in reduced metallic form. 3. The secondary electrochemical cell of claim 1 or 2, wherein the capacity of at least one cathode for absorbing lithium is at least 1.2 times greater than the capacity of at least one anode. The secondary electrochemical cell according to claim 1 or 2, wherein at least one negative electrode has a capacity 1.1 to 2 times larger than the capacity required to absorb the total moving lithium contained in the battery. 3. The secondary electrochemical cell of claim 1 or 2, wherein the amount of mobile lithium in the cell is at least 1.1 times greater than the capacity of at least one anode for absorbing lithium. A battery comprising at least one secondary electrochemical cell according to any one of claims 1 or 2. A method for manufacturing a battery according to claim 6,
At least one positive electrode containing a metal compound capable of reversibly incorporating and releasing lithium in the form of ions,
A mixture of a graphitizable carbon compound capable of reversibly incorporating and releasing lithium in the form of ions and a metal capable of being alloyed with lithium or a mixture of the graphitic carbon compound and a semi- At least one negative electrode containing a metal and a mixture of said semimetals and an electrolyte are combined with the electrochemical cell to form an electrochemical cell,
Regarding the capacity for absorbing lithium, at least one negative electrode is set to a capacity greater than at least one positive electrode, and lithium is introduced into the battery in an amount that exceeds at least 1.2 times the capacity of at least one positive electrode for absorbing lithium And with respect to the capacity for absorbing lithium, at least one negative electrode is set to a capacity for absorbing the total lithium contained in the battery, and the additional moving lithium is set by metal lithium or by pre-lithization of the negative electrode Is provided through a negative electrode by means of a negative electrode. delete 8. The method of claim 7, wherein lithium is introduced into the cell at least partially through the electrolyte by using a conductive salt that is capable of liberating lithium ions from the anode. delete

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